A hydrocarbon producing well typically includes two coaxial conduits connecting the underground hydrocarbon reservoir to the surface. The outer conduit (casing) is set permanently in place while the inner conduit (tubing) is removable. The outer conduit is necessarily larger than the inner conduit. Typically, flow of hydrocarbon to the surface is through the inner conduit. However, in cases where the hydrocarbon reservoir has a large potential to produce both liquid and gases, the size of the inner conduit can significantly restrict the producing gaseous flow. In these cases, it is desirable that both gas and liquid flow through the annular space between the outer and inner conduits, providing a larger flow area and resulting in significantly less restriction to flow and higher flow rates. This is known as annular flow. A problem facing such annular flows relates to flow of separate liquid and gas phases where gas is the predominant phase. In order to flow liquid and gas vertically upward when gas is the predominant phase, the velocity of the gas phase must be high enough to lift all of the liquid to the surface (minimum lift velocity). If the gas velocity is too low, liquid will accumulate in the bottom of the annular space and restrict gaseous flow. Under annular flow conditions with the large flow area, gas velocities are minimized creating the potential for liquid accumulation. This liquid accumulation can ultimately shut off virtually all gas flow.
In these cases, it is possible to produce the well simultaneously up the inner and outer conduits, utilizing a compressor on the inner conduit to increase the gas velocity in the inner conduit to a level sufficient to lift the produced fluids out of the wellbore (to the surface). This process is referred to herein as compressor assisted annular flow (CAAF). However, field testing has shown that CAAF can be difficult to initiate in some wells. As the annulus valve is opened to allow flow up the annulus, the resulting reduction in flowing bottom hole pressure causes an initial slug of liquid to enter the inner conduit and the gas flow rates up the inner conduit with the CAAF compressor running are insufficient to lift the liquid slug out of the wellbore. This results in a log off situation in the inner conduit and the compressor shuts down on low suction. The condition is caused by the fact that minimum lift gas velocities are calculated based on the gas velocity needed to carry small droplets of fluid up the hole (mist flow) rather than the velocity needed to lift larger slugs of fluid.
Therefore, there is an ever-increasing need to develop an apparatus and a method for recovering hydrocarbon through the tubing/casing annulus by modifying the downhole configuration to obtain better mixing of a reservoir's gas and liquid production before splitting flow between the inner and outer conduits. It would also be a significant contribution to the art to provide such an apparatus and a method for flowing a hydrocarbon simultaneously through the larger outer conduit and the smaller inner conduit.